EFFECTS OF HISTAMINE-LIBERATORS 



Anaphylatoxin 



Since the action of histamine-liberators on the dog so closely resembles 

 anaphylactic shock in that species, it seemed of interest to attempt to relate the 

 mast cells and anaphylaxis in the rat. Unfortunately, the rat can hardly be 

 rendered anaphylactic, but the problem was approached by the use of an 

 anaphylatoxic serum. This was prepared exactly as described by Bordet (1913), 

 except that in place of guinea pig serum five parts of rat serum were incubated 



Fig. 22 



Mesentery of rat killed four minutes after the intravenous injection of anaphylatoxin, stained 

 with methylene blue. A group of mast cells shows abnormal swelling and early degranulation. 

 One of these contains a large vacuole, and early vacuolation is also present in the nearby 

 compact cells, which as yet show little swelling (,-, 510). (Riley (1953), /. Path. Bact. 65, 471.) 



for two hours at 37° C. with one part of semi-solid agar. This was then centri- 

 fuged and 1-5 ml. of the supernatant 'serotoxin' were injected intravenously 

 into each of three rats. The outward signs of shock produced by these injec- 

 tions were a mere temporary acceleration of heart rate and respiration. The 

 animals were therefore killed 3-5 minutes later. Despite the minimal clinical 

 evidence of shock, the appearances in the peritoneal spreads closely resembled 

 those seen after the use of histamine-liberators. Thus nearly all type-II cells 

 in the mesentery were swollen and in process of vacuolation or degranulation, 



E 65 



